thomson



I J. THOMSON. ELECTRIC FUMING 0R DlSTiLLlNG FURNACE AND CONDENSERTHEREFOR.

, APPLICATlON FILED OCT- Z1915. 1,193,633. Patented Aug. 8, 1916.

5 SHEETSSHEET I.

1. THOMSON. ELECTRIC FUMING 0R DISTILIJNG FURNACE AND CONDENSERTHEREFOR.

APPLICATION FILED OCT. 2, H5. 1 1 93,633 Patented Aug. 8, 1916.

5 SHEETS-SHEET 2- J. THOMSON. ELECTRIC FUMING 0R DISTILLING FURNACE ANDCONDENSER THEREFOR.

APPLICATION FILED OCT. 2. I915.

a A I m 1; THOMSON. ELECTRIC FUMING 0R DlSTlLLING FURNACE AND CONDENSERTHEREFOR.

APPLICATION FILED OCT- 2. I915.

Patented Aug. 8, 1916.

5 SHEETSSHEET 4.

v drawings, forming a part hereof.

UNITED STATES PATENT OFFICE.

JOHN THOMSON, OF NEW YORK, N. Y., ASSIGNOR T0 JOHN THOMSON PRESSCOMPANY, OF JERSEY CITY, NEW JERSEY, A CORPORATION OF NEW JERSEY.

ELECTRIC FUMING OR DISTILLING FURNACE AND CONDENSER THEREFOR.

T 0 all whom it may concern Be it known that I, JOHN THOMSON, a citizenof the United States, and a resident of the borough of Manhattan of thecity of New York, in the county and State of New York, have inventedcertain new and useful Improvements in Electric Fuming or DistillingFurnaces and Condensers Therefor, of which the following is a specificaton, reference being made to the accompanying This invention relates tothe metallurgy of metals which are capable of being volatilized and thencondensed or precipitated, and the particular object thereof is torefine an impure metal, or alloy, -pro ducing a'high grade of coalescedmetal, or dust, or oxid, as the case may be.

The invention essentially resides in the employment of an electricfurnace of the resistor type and coordinating elements designed toaccomplish the above object in an effective and economical manner.

The general principles involved Wlll be concurrently pointed out withspecial reference to the metallurgy of zinc, in connection with thedescription of the accompanying drawings; which are presented asrepresentative embodiments of the invention.

Figure 1 is atransverse center section of the furnace, viewed as on theline B of Fig. 2, except that its resistor is shown in end elevation,having a metal condenser on its left-hand side and a blue-powder con-. I

forms produced by rods or plates; and with denser, or precipitator, onits right-hand side. Fig. 2 is a longitudinal center section, theresistor and a terminal being shown I in side elevation and being viewedon the line C of Fig. 1. Fig. 3 is a top plan and partial horizontalsection, as viewed from the planes denoted by D and E, of Fig. 1. Fig.4is a top plan view, enlarged, of the terminals, resistor and connector.Fig. 5 is a transverse section of the resistor, as viewed on the line Fof Fig. 4. Figs 6 and 7 are detached sectional views showingmodifications in the cross-sectional form of the resistor. Fig. 8 is adetached view, enlarged, of one of the terminals showing means for watercooling it. Fig. 9 is a detached view developed from the furnacechamber, .as in Fig. 2, showing a modification in the disposal of itsseptum-plates. Fig. 10 is a detached plan view of the liquid.

condenser, enlarged, its cover-plates being Specification of LettersPatent.

Patented Aug. 3, 1916.

Application filed October 2, 1915. Serial No. 53,733.

H or I of Fig. 1'. Fig. 13 is a vertical cross section of theblue-powder condenser or precipitator, as viewed on the line J of Fig.1, except that its water-jackets are shown in end elevation. Fig. 14. isa plan View of the slidable valve for withdrawing blue-powder,

it being shown above in longitudinal section in Fig. 13; and Fig. 15 isan enlarged detail view of an aspirator the application of which isindicated on the blue-powder condenser, Fig. 1.-

The fuming chamber K of the furnace L is heated by a resistor M the typeof which was originally proposed by F. A. J. Fitz Gerald, Elcctroclwmz'cal and Metallurgical Industry, page 215 of 1905; that is acarbon bar or slab 16 or "16 having a series of transverse staggeredslots 16, alternately cut partially through from one side and then fromthe other, thereby producing a zig-zag circuit of limited crosssectional area the resistance of which may usually be sufiiciently highto come within the voltage-range of standardized generators ortransformers. The Fitz Gerald resistor, sometimes termed the zig-zagresistor possesses the unique advantages of being more readilysuspended-and more closely controllable as to its temperature than other.the furnace. The structure is secured together by means of taperedcarbon pins 19,

or. screws may be used if desired. The resistor-slabs instead ofbeingsquare or rectangular in cross section are trapezoids, the beveledsides 20 of which face downwardly, the-bottoms of the slots 21preferably corresponding to the outer angles; 1 Theupper side-faces 22of the zinc-trough 23 are availed of as a support for the ends of thconnector. Consequently, by simply removing the bricks in the end wallof the furnace the resistor complete with its connector ofshort-circuiting. The variation in depth of the bath, as will later bepointed out, is merely nominal, whereby the utmost effectiveness intransfer of heat is realized.

Three particular advantages ensue by forming the resistor-slabs, intheir crosssection, as trapezoids. Thus, see Fig. 5, the transversestability, as respects sagging, is greater than if the sldes of the slaband bottoms of the slots were vertical; the heat is radiated from thesloped sides at a rightangle thereto, that is toward the bath, asdenoted bythe arrows a; the downwardly radiating surface is therebyincreased about 15% and as the transverse length of the circuit, betweeneach slot, corresponds with the angles of the sides, as b maximum, 0mean and d minimum, the greatest currentdensity is along the lower zone,that is to say nearest to the bath and precisely where required.Obviously, if the heat was to be utilized upwardly, or sidewise, theposition of the resistor would be correspondingly reversed. It ispreferable, in practice, if the trapezoidal angles are somewhat acute,to leave a small extent of theupper edges vertical 26, as a sharpintersection is liable to be broken in handling. Fig. 6 denotes thetrapezoidal section developed to about its maximum extent, that islimited by the intersection of the lower edges 27 of the slots, and Fig.7 indicates a modification in which the connecting trapezoidal circuitsections 28 are produced in the form of curvedv segments.

Clos. regulation of the temperature is-of first importance. In using theFitz Gerald .zig-zag type of resistor as a compound element in series,the connector. should have an excess of section over that of therestricted circuit and be thoroughly well attached with a largearea ofsurface contact.

This is well realized, as See Fig. 1, by fit:-

ting the trapezoidal ends to corresponding recesses 28 in the connectorand then keying them together by tapered or threaded pins. Anotherfeature not to be neglected is the water-coolingof the terminals, asthis tends to closeness of temperature regulationas a WllOlQ and avoidstroublesome air burning at or within the brick-work. An effective meansto this end is shown in Figs: 2 and 8,

consisting in boring a relatively deep hole 29 along the axial center ofthe terminal and inserting a metal tube 30 which contains a smalleraxial tube 31 and an outer transverse tube 32. Both ends of the largetube are tightly closed while both ends of the other tubes are open.Cold water is forced in, as arrow e, impinges against the ferent depthsin the terminals. Heat is extracted from the center, where most efietive, and as the pipe-joints may be brazed the system is very safeagainst accidental leakage of water.

The trough 23 is filled and replenished from time to time exclusivelywith melted metal, pre-fused extraneously, which is poured in throughthe chute 33, Figs. 2 and 3, the inner end 34 of which is normallybeneath the surface of the bath, acting as a seal against ingress of airor egress of fume. This mode of charging is most effective, as hot metalcan be fed in small quantity and at relatively short intervals, therebynot' sensibly disturbing the metal in the bath or interfering with therate of fume-evolution; which is a feature of prime importance. Also, inthis manner the depth of the bath may be maintained with slightvariation, say within a fractional part of an inch, as from the levelI). to i, Fig. 2, and the thermal condition with respect'to the resistorwill remainpractically perfect for an indefinite period of time.

It has been found in practice that the most advantageous manner ofconstructing the chute, as see Figs. 2 and 3, is by boring a hole in arod or bar of amorphous carbon or Acheson graphite and disposing it atan pered, the larger diameter being at the bottom. As carbon is a goodconductor of heat, the metal contained within the chute is less liableto freeze; but, if such should occur, the bore being tapered anddisposed as de-' scribed, the solid plug of metal can readily be drivendown into the molten bath. Then, when charging fluid metal, there ismuch less liability of its splashing or disturbing the continuity of thebath than would be the case were the chute set vertically. Incidentally,too, it is much more convenient for utilization as a peep-hole.

The foregoing conditions, that is radiation of heat uniformly to allportions of the bath-surface, the localized blistering effe t producedby the closeness of the resistor to the bath and the very. slightdisturbance caused therein either by convection or charging smallvolumes of hot fluid metal, results in a very important advantage,namely, little if any circulation is caused in the bath, whence itssurface is uniformly the hotter portion thereof. Consequently, asthelatent heat of vaporization of metals, and particularly zinc, is theprincipal source 0 sorption of energy, essentially all of the heatflowing from the resistor to the bath is effectively utilized.

At considerable intervals, depending upon the quantity of foreign mattercontained in the primary charges, the residue must be withdrawn; thebulk of which, in the instance of zinc, being lead, iron, copper, etc.,will ordinarily precipitate to the bottom of the trough.' This isprovided for by the tap-hole 35, 2, or if it is desirable to quicklyempty the trough the plate 36 is removed exposing the larger opening 37As a further means for conserving the heat developed by the resistor,especially that radiated from its upper surface, and also to efiect avery uniform dispersion of the fume into the higher reaches of thefurnace chamber, as O, a septum is provided formed by a series ofrefractory plates 38, Figs. 1, 2 and 3, which may be perforated or setto leave intervening slits 39. The fume, as arrows j, is thereby causedto dis perse and pass uniformly and vertically upward, expanding, as itleaves the slits, into the overhead or sub-chamber whence it willimpinge against the cover, 40; but the heat emitted from the resistorimpacts against the plates a considerable portion of which isnecessarily reflected backwardly, as denoted by arrows is. In any event,depending upon the thickness and character of the plates, theresistor-temperature will be substantially less above the septum and theeffect of this reduction, together with the beforementioned expansion ofthe fume and its impingement upon the cover, serves both to reduce thetemperature of the fume, prior to its entry into the condenser, and alsoto lessen the radiation loss to atmosphere from the outer surface of thecover. Or otherwise stated, the heat radiated to atmosphere, through thecover, is that derived from the fume plus that conducted through theseptum. A modified disposal of the septumplates is shown in Fig. 9,wherein two series of plates 38, 38* are employed, spacedlongitudinally, as 38*, each overhead plate covering an underlyingspace, as 38 of about equal breadth. In this wise, a somewhat more freeand greater area may be furnished for escape of fume and no heatvertically radiated from the resistor will pass directly into the upperchamber.

With the terminals located in the same end of the furnace, the chargingchute and f ab-- surplus fume 1s regained in the form of tions as areresidual port being in the other end, both sides of the furnace are leftentirely free for application of condensers, of which two are shown: aliquid metal condenser Q, on

the left-hand side and a dust or blue-powder condenser P on theright-hand side, these being supplied with fume through the ports 41,42. By means of'the valves 43, i4, either condenser may be operatedindependently of the other, or a pair of metal condensers, or of dustcondensers, may be employed. There are, however, certain advantages tobe derived in operating one of each kind. For example, as between avariable supply of power, and a cold, dry atmosphere or a warm moistatmosphere, there may be times when the rate offuming or of condensationwill be out of balance. If the capacity of the metal condenser is lessthan that of the fuming capacity of the furnace, then the valve A may besomewhat opened, as shown, whereby the furnace can be run at its highestrate, the metal condenser taking all that it can coalesce into fluidwhile the dust or oxid. The aforesaid valves are also utilizable whenboth condensers are of the same character and employed for the samepurpose, in that if one runs ahead of the other, so to speak, they canthereby be quickly brought into a state of balance.

The condensers here shown embody certain principles which have alreadybeen set forth in patents previously granted to the present applicant;but with the reservation that those cases related to zinc smeltingoperations wherein fume is produced by chemical reaction between ore andcarbon as a reagent and is combined with monoxid of carbon, the volumeof which, at the instant of evolution, is approximately equal to that ofthe zinc-fume and is not diminished in volume except by a partialwithdrawal of its heat. Therefore, the details in this application willbe restricted to such adaptaparticularly applicable to a distillingfurnace, in which essentially no gas or vapor is produced other thanmetallic fume. WVhich is to say, this means that a condenser, whetheradapted to produce liquid metal or dust would be operating theoreticallyperfectly when taking fume at its entrance at full capacity, under suchhead or pressure as might be necessary to cause it to adequately flow,while at the extremity there would be no volume other than thatof theliquid metal produced and no pressure. P67 contra, if the enteringvolume is completely condensed before the exit is reached, then theremay be a vacuous condition and, if the conditions permit, an opposingback-pressure from atmosphere may result.

Having regard to the foregoing principles and referring to Figs. 1 and3, the metal 30 way 50. The several plates are preferably slid along therod to produce spaces between them which gradually diminish the area ofthe lateral flow-ways-from the inner to the outer end of the chamber.Consequently, the velocity of the fume and the area of plate-surface aremaintained approximately constant from inlet to outlet. This produces aflow along a general horizontal plane during which the fume is subjectedto numerous impingements, expansions, contractions and deflections, asdenoted bv the arrows m, and establish conditions which are highlyconducive to the condensation and coalescence of fume, into liquidmetal. A more complete practical development of these principles isshown in Figs. 10 and 11, in which between the baflle-plates 48 othershorter plates 51 are set to produce gradually diminishing spaces, thefume flowing therethrough in parallel, as the arrows denote. When liquidmetal is accumulated, as 52, Fig. 1, the

lower portions of the plates are immersed' therein; therefore, the floorof the chamber becomes in reality a large surface of fluidified metalwhich performs the double function of stabilizing the proper temperaturein the plates and affording an affinitive medium for coalescence offume. In the assemblage, it is important to observe that the alternateends of the baffle-plates are in contact with the side-walls and thesame refers to the cover-plates of the condensing chamber, whereby torapidly conduct heat from the interior to the exterior. It may here beobserved that, in practice, the condenser is set on a downward slope.

Referring now to Figs. 1, 3 and 12, it will be perceived that thecondenser is supported on three narrow brick ledges, 53, 54, 55, betweenside-walls, 56, 57, set to leave vertical free spaces, 56, 57 In thiswise, nearly the entire outer surface of the condenser is, or may be,freely exposed to atmosphere; but the extent of heat-radiation issusceptible of complete control by means of the simple expedient ofplacing or removing heat insulating sheets, wooden boards or the like,over the top, as 58, beneath, as 60. At the initial start of thefurnace, for the distillation of zinc, it is highly essential topre-heat the interior of the condenser, every portion and part of it, toa temperature well above that of the melting point of spelter, else moreor less of blue-powder will be initially formed and accumulated. Also,

such as asbestos,

59, and across the front, as,-

in the event of a temporary cessation of the fume-supply, as whenwithdrawing residual matter from the trough, it is of the firstimportance to be able to promptlyapply external heat to the condenserand maintain its interior at a temperature above that at whichblue-powder may be produced. To this end, preferably two auxiliaryresistors are disposed in channels, 63, 64., beneath the condenser. Forthis purpose the resistor may be a bed of broken carbon, as depicted byIV in Fig. 12, interpolated between terminals, 65, 66. Thus, current mayquickly be turned on, either to one or both, and the desired temperaturebe imparted and maintained indefinitely, whether the fuming furnace isin operation or not.

Reference should now be had to Figs. 1, 3, 13 and 14. In theblue-powder, or dust, condenser P (perhaps the word precipitator is themore exact term) the same fundamental principles inhere but the mode ofexecution is quite divergent from that of the liquid condenser. Itsfume-chamber T' is formed by a sheet-metal casing 67 the lower edge ofwhich rests within the flanged recess 68 of a cast iron casing 69, intowhich the blue-powder 7O gravitates and is collected. The top of saidfume-chamber is inclosed by a flat metal plate 71 which need not berigidly confined, whereby in the event of an explosion it will freelyblow off. Tight joints are effected as by means of cement 72, orinterposed gaskets may be used. Within said chamber are a series ofbaffle-plates 73 preferably curved in crosssection toward the inflowingfume, all being conveniently strung on two free rods, 74, 75, as in theinstance previously described. On each outside of the casing, and incontact therewith, is a sheet-metal water-tank, as 7 6, 77, which mayreston the flange of the cast iron casing. These tanks may be open attheir tops, as shown. The nipples, 78, 7 8 and 7 9, 7 9 are forattachment of rubber tubing to supply cold water and withdraw it whenwarm, or water may be continuously circulated, as may be desired. In itsdimensions, the width of this fume chamber is relatively substantiallvless than its height and length, in fact generally following the designof the metal condenser except that it stands in its lesser dimensionvertically instead of horizontally. Following the courses denoted by theflow-arrows n, it will be perceived that the fume, as it is receivedfrom the furnace, suffers a considerable expansion and is thereaftercaused to flow forth and back across the baflle-plates and to acutelyimpinge against andflow along the watercooled sides of the casing. As aconsequence, a large volume of fume may be chilled with great rapidity;which is then free to immediately gravitate into the underlyingcollecting chamber Z from whence it is intermittently withdrawn by theslidable valve 80. As shown, this valve is a simple block having anopening 81 mounted in a slide-way blue-powder in the metal condenser isvery objectionable; and it should be borne in mind that the productionof dust is contingent upon a chilling temperature, that is a temperature'less than the melting point of zinc. Yet, blue-powder may be andusually is produced in an oxidizing atmosphere. The presence of oxid ofzinc (ZnO) is still more objectionable and this refers either to themetal condenser or to the blue-powder condenser. The formation of ZnO,however, involves the presence of air in considerable volume and is moreor less independent of the temperature. The blue-powder ofcommercehitherto has been nearly if not entirely a residual by-productand the opinion is generally held that even the most infinitesimal ofits globules is imprisoned in a film of oxid. So being, it is an oxid ofzinc in which the content of oxygen is a minimum. But when theproduction is by distillation from metal, whether pure or impure, andthe contaminating effects of C0, C0 hydrous vapor or atmospheric air areexcluded, both in the fuming furnace and the condenser, then there canbe no oxidization; there is no coloring of blue due to the oxid and theproduct is a pure grayish zinc-dust, the particles of which areexceedingly minute. Consequently, graydust is much purer and moreeffective in several of its applications in the arts than ordinaryblue-powder. The latter is classed, commercially, as an explosive;gray-dust, ridden of its protecting films of oxid, is considerably moreexplosive.

The foregoing premises lead to the concluding coordinating element ofthe present application, denoted in Figs. 1 and 15, consisting in anaspirator Y for inductively exhausting "air from the furnace and thecondensers and also for positively maintaining therein a slightlyvacuous condition; or, otherwise expressed, a condition of minortensionwhich shall be somewhat less than that of atmospheric pressure. Thiseffect is produced by the simple expedient of supplying a vertical tube83, screwed upon a nipple 84, applied to a condenser cover or plate 47,71, and having thereon one, two or more inciting-tubes, as 85, 86,declined from the horizontal at an angle or angles of about 45. Now, byconnecting these inciting tubes, as by means of rubber tubing, withmeans for supplying air under pressure, any contained air, or gas, orfume, or combination thereof, will beforcibly driven upwardly and out ofthe main tube 83, as see arrow '0', by the impulse of the jet or jets,and a vacuous condition will necessarily be produced below, therebycausing an induced flow from within the condenser, as denoted by arrowm. If an excess of uncondensed fume reaches the far end of thecondenser, the aspirator need not be used; for, by simply shutting offthe inciting air, it will then serve as a free outlet, or burner, in theusual manner. This device may also be availed of when first starting thefurnace, as a somewhat pronounced inductive effect may be producedwhereby to withdraw a portion of the contained air and cause it to bemore quickly displaced by hot fume than would otherwise be the case. Butthis latter use of an aspirator, that is to remove the relatively largevolume of air primarily contained in the furnace and condensers, iscomparatively limited in that if a sufficient vacuum were produced afresh supply of air would doubtless be drawn in through the brickwork.Consequently, a means has been developed for this purpose; whichconsists either in producing within the furnace an inert gas, formed,say, by an oil containing a minimum content of carbon, or by making sucha gas externally and conveniently introducing it through the chargingchute, thereafter or prior thereto inserting fluid metal. The result ofthis procedure is that essentially all of the air is displaced by thegas, finding vent through the condenser openings; then as fume isproduced it in turn displaces the gas, whence no oxid of the metal willbe formed.

A general feature of the design which has purposesly not been earlieradverted to but is ofthe first importance relates tothe large heatradiating surface of the resistor with respect to the heat absorbingsurface of the bath. In practice, these may be about equal. Therefore,as thetemperature of the resistor will be nearly if not entirely uniformat every square inch of its surface, there will be no hot spots over thebath; the evolution of fume will proceed with great uniformity and allthe ra idity at which calories may be supplied an absorbed. This meansthat the temperature at and upon the surface of the bath need never be,nor can it well be, but little if any above,the free boiling point ofthe metal to be vaporized. This also means that all other lower portionsof the bath will be at a lesser temperature; hence, when zinc is beingdistilled, metals like lea-d, tin, copper and iron will not bevaporized, (as may occur in hot-spot zones) and they will tend to settleout of the relatively thin boiling plane, according to their respectivedensities. And factors not to be overlooked in the above connection arethe coordinating performances of the sloped chute, whereby smallquantities of hot fluid may frequently be charged without suspending theproduction of fume and without seriously disturbing the bath; also theseptum plates which at once afford a very rapid and unobstructed flowfrom the fuming chamber and yet prevent superheating of the fume withthe contingent loss of energy which would therebyensue.

Various modifications, or even substitutions, may be made in the detailswithout departing from, or evading, the spirit and essence of thisinvention. For example, while it is contended that the type, form anddisposal of the zig-zag resistor herein described is distinctly the bestfor the contemplated purpose, yet it is not per se a pre-requisite whentaken in connection with some of its co-' ordinating functions. It maybe operated in parallel; or may be double-compounded; or resistorsformed by rods, interlocking plates and broken carbon sustained ongratebars might be substitutedwhich would leave certain other elementsof the invention as they stand. The elongated trough may be madeapproximately square or in the form of an ovoidal basin. The singlecharging chute may be variously disposed, even to supplying the moltenmetal centrally, between the resistor slabs, or a plurality of chutesmay be employed.

Brief mention has herein been made that the furnace may be used forproducing oxids, such as of zinc, ZnO. Such is, in fact, entirelyfeasible, but the means of its production from pure fume has not beenshown in that the principles involved and the elements required are inmany respects dissimilar from the more closely coordinating functions ofmetal and dust condensers.

lVhile a complete citation of various other purposes to which featuresof this invention can be applied will be omitted, this is not to beconstrued as indicating that the intimated utilizations have escaped dueconsideration, and it may be pointed out, in conformity with the openingparagraphs, that this system is well adapted for the treatment of metalsother than zinc which are capable of being vaporized and thereaftercondensed or precipitated in the form of coalesced metal, dust, or oxid,such say, as cadmium, lead, antimony, etc. Moreover, when an alloy ofvarious metals is charged, each having a distinct vaporizingtemperature, the operation may be carried on, in effect, byfractional-distillation. Thus, as a single example, taking an alloy ofzinc and lead, the

former may first be coalesced at its lower fuming temperature while thelatter may be later vaporized at its considerably high fumingtemperature.

lVhat I claim is 1. A zig-zag plate-resistor, its inner end, or ends,being attached to and sustained by a bar, or connector, resting uponledges in the furnace and along which the said bar or connector may beslid in or out.

2. A zig-zag plate-resistor having a cross section in the form of atrapezoid, the sideangles of which are presented to the surface, or inthe direction, where the radiated heat is to be utilized.

3. A zig-zag plate-resistor the cross-section of which is such that thecurrent-density is greatest at or near to the surface, or surfaces, fromwhich its radiated heat is utilized.

4. A zig-zag plate-resistor the cross-section of which is in the form ofa trapezoid having its greatest current-density in a horizontal zonebetween the lower portions of the converging sides.

5. An electric fuming furnace having the following elements disposed inhorizontal zones and in the order named: a trough containing a bath ofmolten metal; a zig-zag resistor whose heat is radiated downwardly andupwardly; a system of spaced or perforated plates and an over-lyingchamber into which the ascending fume flows and expands.

6. An electric fuming furnace having a trough containing molten metal, aresistor horizontally suspended above the trough, a spaced septumhorizontally suspended above the resistor and a free space above theseptum for receiving the vaporized products.

7. An electric fuming furnace having a trough containing molten metal, aresistor above the trough, a portion of whose heat is radiated upwardlyand a septum composed of spaced plates suspended above the resistorthrough which fume may freely escape but by which the upwardly radiatedheat is considerably reflected toward its original source.

8. An electric fuming furnace having a resistor-chamber divided by aseptum composed of spaced plates horizontally situated between theresistor and the outlet port or ports leading to the condensing system,the construction and arrangement being such that the fume is caused toprimarily disperse and flow uniformly into all portions of thesub-chamber from which the said condensing system is supplied.

9. An electric fuming furnace having a liquid metal condenser providedwith a series of bafiie-plates so disposed as to cause the fume to flowforth and back, but progressively forward, along a general horizontalplane; the fiow-spaces between the plates becoming less and less fromthe inlet to the outlet.

10. An electric fuming furnace having a liquid metal condenser having aseries of baffle-plates and one or a plurality of interposed spacedshorter plates, whereby the fume, between pairs of bafiie-plates, iscaused to flow through the spaces in parallel.

11. An electric fuming furnace having a liquid metal condenser providedwith plates for causing a sinuous flow of fume; the flowspacesdiminishing and the area of surfacecontact increasing from inlet tooutlet.

12. An electric fuming furnace having a condenser provided with platesfor producing a sinuous flow of fume, the said plates being strung uponand sustained by a free rod or rods.

13. An electric fuming furnace having a liquid metal condenser,relatively shallow with respect to its other dimensions, provided with aplate-system for producing a sinuous flow of. fume along acontinuoushorizontal plane, the condensed metal forming a bath in which the lowerportions of all the plates are immersed and a floor over whichuncondensed fume is caused to continuously flow.

14. An electric fuming furnace having a liquid metal condenser,relatively shallow with respect to its other dimensions, pro vided witha plate-system for producing a sinuous flow of fume, the upper and loweredges and one end of said plates being in physical contact with thecondenser-casin 15. An electric fuming furnace having a liquid metalcondenser set in brick-work having underlying channels in whichresistors and suitable terminals are disposed for primarily orintermittently heating the said condenser to a temperature above that atwhich the fume will be precipitated in the form of dust, and means forquickly intercepting the heat flowing from said resistors to thecondenser.

16. An electric fuming furnace having a condenser for producing dust, inthe interior of which are a series of curved or bent bafiieplates, theinner surfaces of the curvatures being opposed to the fume-flow.

17. In an electric metallic distilling furnace, a coalescing metalcondenser on one side and a dust condenser, or precipitator, on theother side, and controlling valves in each entry port, whereby one ofsaid condensers may be operated to its full capacity while the other maytake any surplus of fume, if such exists.

18. In an electric zinc distilling furnace, an aspirator applied to thefar end of its condenser, or condensers, comprised in an open verticaltube having a plurality of declined inciting tubes to which air underpressure is conducted, whereby a regulatable flow may be induced fromthe interior of the said condenser, or condensers.

19. In an electric zinc distilling furnace, an aspirator applied to thefar end of its condenser, or condensers, comprised in a main openvertical tube having a plurality of declined inciting tubes, the maintube being applied to a nipple in the condenser cover, whereby when aninduced flow is not required the aspirator may be left in place and usedas a Vent or burner.

This specification signed and witnessed this 30th day of September, A.D., 1915.

JOHN THOMSON.

Signed in presence of RALPH M. THOMSON, J. R. AGNEW.

